While psychological knowledge is often applied to the assessment and treatment of mental healthproblems, it is also directed towards understanding and solving problems in several spheres of human activity. By many accounts psychology ultimately aims to benefit society.[7][8] The majority of psychologists are involved in some kind of therapeutic role, practicing in clinical, counseling, or school settings. Many do scientific research on a wide range of topics related to mental processes and behavior, and typically work in university psychology departments or teach in other academic settings (e.g., medical schools, hospitals). Some are employed in industrial and organizational settings, or in other areas[9] such as human development and aging, sports, health, and the media, as well as in forensic investigation and other aspects of law.

Etymology

The word psychology derives from Greek roots meaning study of the psyche, or soul (ψυχήpsukhē, "breath, spirit, soul" and -λογία -logia, "study of" or "research").[10] The Latin word psychologia was first used by the Croatianhumanist and LatinistMarko Marulić in his book, Psichiologia de ratione animae humanae in the late 15th century or early 16th century.[11] The earliest known reference to the word psychology in English was by Steven Blankaart in 1694 in The Physical Dictionary which refers to "Anatomy, which treats the Body, and Psychology, which treats of the Soul."[12]

In China, psychological understanding grew from the philosophical works of Laozi and Confucius, and later from the doctrines of Buddhism. This body of knowledge involves insights drawn from introspection and observation, as well as techniques for focused thinking and acting. It frames the universe as a division of, and interaction between, physical reality and mental reality, with an emphasis on purifying the mind in order to increase virtue and power. An ancient text known as The Yellow Emperor's Classic of Internal Medicine identifies the brain as the nexus of wisdom and sensation, includes theories of personality based on yin–yang balance, and analyzes mental disorder in terms of physiological and social disequilibria. Chinese scholarship focused on the brain advanced in the Qing Dynasty with the work of Western-educated Fang Yizhi (1611–1671), Liu Zhi (1660–1730), and Wang Qingren (1768–1831). Wang Qingren emphasized the importance of the brain as the center of the nervous system, linked mental disorder with brain diseases, investigated the causes of dreams and insomnia, and advanced a theory of hemispheric lateralization in brain function.[16]

Distinctions in types of awareness appear in the ancient thought of India, influenced by Hinduism. A central idea of the Upanishads is the distinction between a person's transient mundane self and their eternal unchanging soul. Divergent Hindu doctrines, and Buddhism, have challenged this hierarchy of selves, but have all emphasized the importance of reaching higher awareness. Yoga is a range of techniques used in pursuit of this goal. Much of the Sanskrit corpus was suppressed under the British East India Company followed by the British Raj in the 1800s. However, Indian doctrines influenced Western thinking via the Theosophical Society, a New Age group which became popular among Euro-American intellectuals.[17]

Psychology was a popular topic in Enlightenment Europe. In Germany, Gottfried Wilhelm Leibniz (1646–1716) applied his principles of calculus to the mind, arguing that mental activity took place on an indivisible continuum—most notably, that among an infinity of human perceptions and desires, the difference between conscious and unconscious awareness is only a matter of degree. Christian Wolff identified psychology as its own science, writing Psychologia empirica in 1732 and Psychologia rationalis in 1734. This notion advanced further under Immanuel Kant, who established the idea of anthropology, with psychology as an important subdivision. However, Kant explicitly and notoriously rejected the idea of experimental psychology, writing that "the empirical doctrine of the soul can also never approach chemistry even as a systematic art of analysis or experimental doctrine, for in the manifold of inner observation can be separated only by mere division in thought, and cannot then be held separate and recombined at will (but still less does another thinking subject suffer himself to be experimented upon to suit our purpose), and even observation by itself already changes and displaces the state of the observed object." Having consulted philosophers Georg Friedrich Wilhelm Hegel and Johann Friedrich Herbart, in 1825 the Prussian state established psychology as a mandatory discipline in its rapidly expanding and highly influential educational system. However, this discipline did not yet embrace experimentation.[18] In England, early psychology involved phrenology and the response to social problems including alcoholism, violence, and the country's well-populated mental asylums.[19]

Beginning of experimental psychology

Wilhelm Wundt (seated) with colleagues in his psychological laboratory, the first of its kind.

Gustav Fechner began conducting psychology research in Leipzig in the 1830s, studying psychophysics and articulating the principle that human perception of a stimulus varies logarithmically according to its intensity.[20] Fechner's 1950 Elements of Psychophysics challenged Kant's stricture against quantitative study of the mind.[18] In Heidelberg, Hermann von Helmholtz conducted parallel research on sensory perception, and trained physiologist Wilhelm Wundt. Wundt, in turn, came to Leipzig University, establishing the psychological laboratory which brought experimental psychology to the world. Wundt focused on breaking down mental processes into the most basic components, motivated in part by an analogy to recent advances in chemistry, and its successful investigation of the elements and structure of material.[21]Paul Flechsig and Emil Kraepelin soon created another influential psychology laboratory at Leipzig, this one focused on more on experimental psychiatry.[18]

A different strain of experimentalism, with more connection to physiology, emerged in South America, under the leadership of Horacio G. Piñero at the University of Buenos Aires.[29] Russia, too, placed greater emphasis on the biological basis for psychology, beginning with Ivan Sechenov's 1873 essay, "Who Is to Develop Psychology and How?" Sechenov advanced the idea of brain reflexes and aggressively promoted a deterministic (contra free will) viewpoint on human behavior.[30]

Disciplinary consolidation

One of the earliest psychology societies was La Société de Psychologie Physiologique in France, which lasted 1885–1893. The first meeting of the International Congress of Psychology took place in Paris, in August 1889, amidst the World's Fair celebrating the centennial of the French Revolution. William James was one of three Americans among the four hundred attendees. The American Psychological Association was founded soon after, in 1892. The International Congress continued to be held, at different locations in Europe, with wider international participation. The Sixth Congress, Geneva 1909, included presentations in Russian, Chinese, and Japanese, as well as Esperanto. After a hiatus for World War I, the Seventh Congress met in Oxford, with substantially greater participation from the war-victorious Anglo-Americans. In 1929, the Congress took place at Yale University in New Haven, Connecticut, attended by hundreds of members of the American Psychological Association[22] Tokyo Imperial University led the way in bringing the new psychology to the East, and from Japan these ideas diffused into China.[23][16]

Early practitioners of experimental psychology distinguished themselves from parapsychology, which in the late nineteenth century enjoyed great popularity (including the interest of scholars such as William James), and indeed constituted the bulk of what people called "psychology". Parapsychology, hypnotism, and psychism were major topics of the early International Congresses. But students of these fields were eventually ostractized, and more or less banished from the Congress in 1900–1905.[22] Parapsychology persisted for a time at Imperial University, with publications such as Clairvoyance and Thoughtography by Tomokichi Fukurai, but here too it was mostly shunned by 1913.[23]

After the Russian Revolution, psychology was heavily promoted by the Bolsheviks as a way to engineer the "New Man" of socialism. Thus, university psychology departments trained large numbers of students, for whom positions were made available at schools, workplaces, cultural institutions, and in the military. An especial focus was pedology, the study of child development, regarding which Lev Vygotsky became a prominent writer. Although pedology fell out of favor in 1936, psychology maintained its privileged position as an instrument of the Soviet state.[30] In Germany after World War I, psychology held institutional power through the military, and subsequently expanded along with the rest of the military under the Third Reich.[18]

In 1920, Édouard Claparède and Pierre Bovet created a new applied psychology organization called the International Congress of Psychotechnics Applied to Vocational Guidance, later called the International Congress of Psychotechnics and then the International Association of Applied Psychology.[22] The world federation of national psychological societies is the International Union of Psychological Science, founded in 1951 under the auspices of UNESCO, the United Nations cultural and scientific authority.[33][22] Psychology departments have since proliferated around the world, based primarily on the Euro-American model.[17][33] Since 1966, the Union has published the International Journal of Psychology.[22] Membership in the American Psychological Association increased from 5,000 in 1945 to 100,000 in the present day.[25]

Behaviorism

An early researcher into psychological conditioning was Ivan Pavlov, known best for inducing dogs to salivate in the presence of a stimulus previous linked with food. As the star of psychology rose over the Soviet Union, Pavlov became a leading figure and attracted many followers, who applied his theories to humans.[30] In the United States, "connectionism" studies were conducted by Edward Lee Thorndike, who trapped animals in "puzzle boxes" and rewarded them for escaping. Like Pavlov, Thorndike focused narrowly on stimulus-response (S–R) pairings. He believed that the field of human psychology should focus on outward behavior, writing in 1911: "There can be no moral warrant for studying man's nature unless the study will enable us to control his acts."[34]John B. Watson, teaching at Johns Hopkins, led a rising tide of sentiment in the United States against the idea that psychology had to study consciousness itself. From 1910–1913 the American Psychological Association went through a sea change of opinion, away from mentalism and towards "behavioralism", and in 191 Watson coined the term behaviorism for this school of thought.[35] Behaviorism, embraced and extended by Clark L. Hull, Edward C. Tolman, Edwin Guthrie and many others, focused on the way organisms respond to environmental stimuli eliciting pain or pleasure.[25]

Behaviorism became a dominant school of thought in the midcentury United States, with B.F. Skinner its leading intellectual. Skinner's behaviorism shared with its predecessors a philosophical inclination toward positivism, determinism, and the study of observable behavior.[36][37] In lieu of probing an "unconscious mind" that underlies unawareness, behaviorists spoke of the "contingency-shaped behaviors" in which unawareness becomes outwardly manifest.[36] Notable incidents in the history of behaviorism are John B. Watson's Little Albert experiment which applied classical conditioning to the developing human child, and the clarification of the difference between classical conditioning and operant (or instrumental) conditioning, first by Miller and Kanorski and then by Skinner.[38][39] Skinner's version of behaviorism emphasized operant conditioning, through which behaviors are strengthened or weakened by their consequences.

Noam Chomsky delivered an influential critique of behaviorism on the grounds that it could not adequately explain the complex mental process of language acquisition.[40][41]Martin Seligman and colleagues discovered that the conditioning of dogs led to outcomes ("learned helplessness") that opposed the predictions of behaviorism.[42][43] Skinner's behaviorism did not die, perhaps in part because it generated successful practical applications.[40]

The Association for Behavior Analysis International was founded in 1974 and by 2003 had members from 42 countries. The field has been especially influential in Latin America, where it has a regional organization known as ALAMOC: La Asociación Latinoamericana de Análisis y Modificación del Comportamiento. Behaviorism also gained a strong foothold in Japan, where it gave rise to the Japanese Society of Animal Psychology (1933), the Japanese Association of Special Education (1963), the Japanese Society of Biofeedback Research (1973), the Japanese Association for Behavior Therapy (1976), the Japanese Association for Behavior Analysis (1979), and the Japanese Association for Behavioral Science Research (1994).[44] Today the field of behaviorism is also commonly referred to as behavior modification or behavior analysis.[44]

Psychoanalysis

Beginning in the 1890s, Austrian psychologists including Josef BreuerAlfred Adler, Otto Rank, and most prominently Sigmund Freud, developed an influential school of thought and clinical practice called psychoanalysis. Psychoanalysis comprises a method of investigating the mind and interpreting experience; a systematized set of theories about human behavior; and a form of psychotherapy to treat psychological or emotional distress, especially unconscious conflict.[45] Freud's psychoanalytic theory was largely based on interpretive methods, introspection and clinical observations. It became very well known, largely because it tackled subjects such as sexuality, repression, and the unconscious mind as general aspects of psychological development. These were largely considered taboo subjects at the time, and Freud provided a catalyst for them to be openly discussed in polite society. Clinically, Freud helped to pioneer the method of free association and a therapeutic interest in dream interpretation.[46][47]

Psychoanalytic theory and therapy were criticized by psychologists such as Hans Eysenck, and by philosophers including Karl Popper. Popper, a philosopher of science, argued that psychoanalysis had been misrepresented as a scientific discipline,[48] whereas Eysenck said that psychoanalytic tenets had been contradicted by experimental data. By the end of 20th century, psychology departments in American universities had become scientifically oriented, marginalizing Freudian theory and dismissing it as a "desiccated and dead" historical artifact.[49] Meanwhile, however, researchers in the emerging field of neuro-psychoanalysis defended some of Freud's ideas on scientific grounds,[50] while scholars of the humanities maintained that Freud was not a "scientist at all, but ... an interpreter."[49]

Existential-humanistic theories

Psychologist Abraham Maslow in 1943 posited that humans have a hierarchy of needs, and it makes sense to fulfill the basic needs first (food, water etc.) before higher-order needs can be met.[51]

In the 1950s and 1960s, largely influenced by the work of German philosopher Martin Heidegger and Danish philosopher Søren Kierkegaard, psychoanalytically trained American psychologist Rollo May pioneered an existential branch of psychology, which included existential psychotherapy, a method of therapy that operates on the belief that inner conflict within a person is due to that individual's confrontation with the givens of existence. Swiss psychoanalyst Ludwig Binswanger and American psychologist George Kelly may also be said to belong to the existential school.[54]

Existential psychologists differed from more "humanistic" psychologists in their relatively neutral view of human nature and their relatively positive assessment of anxiety.[55] Existential psychologists emphasized the humanistic themes of death, free will, and meaning, suggesting that meaning can be shaped by myths, or narrative patterns,[56] and that it can be encouraged by an acceptance of the free will requisite to an authentic, albeit often anxious, regard for death and other future prospects.

Cognitive revolution

Starting in the 1950s, the experimental techniques developed by Wundt, James, Ebbinghaus, and others re-emerged as experimental psychology became increasingly cognitivist—concerned with information and its processing—and, eventually, constituted a part of the wider cognitive science.[59] In its early years, this development was seen as a "revolution,"[59] as cognitive science both responded to and reacted against then-popular theories, including psychoanalytic and behaviorist theories.

Noam Chomsky helped to launch a "cognitive revolution" in psychology when he criticized the behaviorists' notions of "stimulus", "response", and "reinforcement". Chomsky argued that such ideas—which Skinner had borrowed from animal experiments in the laboratory—could be applied to complex human behavior, most notably language acquisition, in only a superficial and vague manner. The postulation that humans are born with the instinct or "innate facility" for acquiring language posed a challenge to the position that all behavior, including language, is contingent upon learning and reinforcement.[60]Social learning theorists, such as Albert Bandura, argued that the child's environment could make contributions of its own to the behaviors of an observant subject.[61]

The Müller–Lyer illusion. Psychologists make inferences about mental processes from shared phenomena such as optical illusions.

Meanwhile, technological advances helped to renew interest and belief in the mental states and representations—i.e., cognition—that had fallen out of favor with behaviorists. English neuroscientist Charles Sherrington and Canadian psychologist Donald O. Hebb used experimental methods to link psychological phenomena with the structure and function of the brain. With the rise of computer science and artificial intelligence, analogies were drawn between the processing of information by humans and information processing by machines. Research in cognition had proven practical since World War II, when it aided in the understanding of weapons operation.[62] By the late 20th century cognitivism had become the dominant paradigm of psychology, and cognitive psychology emerged as a popular branch.

Assuming both that the covert mind should be studied, and that the scientific method should be used to study it, cognitive psychologists set such concepts as subliminal processing and implicit memory in place of the psychoanalytic unconscious mind or the behavioristic contingency-shaped behaviors. Elements of behaviorism and cognitive psychology were synthesized to form the basis of cognitive behavioral therapy, a form of psychotherapy modified from techniques developed by American psychologist Albert Ellis and American psychiatrist Aaron T. Beck. Cognitive psychology was subsumed along with other disciplines, such as philosophy of mind, computer science, and neuroscience, under the cover discipline of cognitive science.

Biological

MRI depicting the human brain. The arrow indicates the position of the hypothalamus.

Biological psychology or behavioral neuroscience is the study of the biological substrates of behavior and mental processes. There are different specialties within behavioral neuroscience. For example, physiological psychologists use animal models, typically rats, to study the neural, genetic, and cellular mechanisms that underlie specific behaviors such as learning and memory and fear responses.[63]Cognitive neuroscientists investigate the neural correlates of psychological processes in humans using neural imaging tools, and neuropsychologists conduct psychological assessments to determine, for instance, specific aspects and extent of cognitive deficit caused by brain damage or disease.

Clinical

Clinical psychologists work with individuals, children, families, couples, or small groups.

Clinical psychology includes the study and application of psychology for the purpose of understanding, preventing, and relieving psychologically based distress or dysfunction and to promote subjective well-being and personal development. Central to its practice are psychological assessment and psychotherapy, although clinical psychologists may also engage in research, teaching, consultation, forensic testimony, and program development and administration.[64] Some clinical psychologists may focus on the clinical management of patients with brain injury—this area is known as clinical neuropsychology. In many countries, clinical psychology is a regulated mental health profession.

The work performed by clinical psychologists tends to be influenced by various therapeutic approaches, all of which involve a formal relationship between professional and client (usually an individual, couple, family, or small group). The various therapeutic approaches and practices are associated with different theoretical perspectives and employ different procedures intended to form a therapeutic alliance, explore the nature of psychological problems, and encourage new ways of thinking, feeling, or behaving. Four major theoretical perspectives are psychodynamic, cognitive behavioral, existential–humanistic, and systems or family therapy. There has been a growing movement to integrate the various therapeutic approaches, especially with an increased understanding of issues regarding culture, gender, spirituality, and sexual orientation. With the advent of more robust research findings regarding psychotherapy, there is evidence that most of the major therapies are about of equal effectiveness, with the key common element being a strong therapeutic alliance.[65][66] Because of this, more training programs and psychologists are now adopting an eclectic therapeutic orientation.[67][68][69][70][71]

Comparative

Comparative psychology refers to the scientific study of the behavior and mental processes of non-human animals, especially as these relate to the phylogenetic history, adaptive significance, and development of behavior. Research in this area addresses many issues, uses many methods, and explores the behavior of many species, from insects to primates. It is closely related to other disciplines that study animal behavior such as ethology.[72] Research in comparative psychology sometimes appears to shed light on human behavior, but some attempts to connect the two have been quite controversial, for example the Sociobiology of E. O. Wilson.[73] Animal models are often used to study neural processes related to human behavior, e.g. in cognitive neuroscience.

Developmental

Developmental psychologists would engage a child with a book and then make observations based on how the child interacts with the object.

Mainly focusing on the development of the human mind through the life span, developmental psychology seeks to understand how people come to perceive, understand, and act within the world and how these processes change as they age. This may focus on cognitive, affective, moral, social, or neural development. Researchers who study children use a number of unique research methods to make observations in natural settings or to engage them in experimental tasks. Such tasks often resemble specially designed games and activities that are both enjoyable for the child and scientifically useful, and researchers have even devised clever methods to study the mental processes of infants. In addition to studying children, developmental psychologists also study aging and processes throughout the life span, especially at other times of rapid change (such as adolescence and old age). Developmental psychologists draw on the full range of psychological theories to inform their research.

Educational and school

An example of an item from a cognitive abilities test used in educational psychology.

Educational psychology is the study of how humans learn in educational settings, the effectiveness of educational interventions, the psychology of teaching, and the social psychology of schools as organizations. The work of child psychologists such as Lev Vygotsky, Jean Piaget, Bernard Luskin, and Jerome Bruner has been influential in creating teaching methods and educational practices. Educational psychology is often included in teacher education programs in places such as North America, Australia, and New Zealand.

School psychology combines principles from educational psychology and clinical psychology to understand and treat students with learning disabilities; to foster the intellectual growth of gifted students; to facilitate prosocial behaviors in adolescents; and otherwise to promote safe, supportive, and effective learning environments. School psychologists are trained in educational and behavioral assessment, intervention, prevention, and consultation, and many have extensive training in research.[74]

Evolutionary

Evolutionary psychology examines psychological traits—such as memory, perception, or language—from a modern evolutionary perspective. It seeks to identify which human psychological traits are evolved adaptations, that is, the functional products of natural selection or sexual selection. Evolutionary psychologists suggest that psychological adaptations evolved to solve recurrent problems in human ancestral environments. By focusing on the evolution of psychological traits and their adaptive functions, it offers complementary explanations for the mostly proximate or developmental explanations developed by other areas of psychology (that is, it focuses mostly on ultimate or "why?" questions, rather than proximate or "how?" questions).

Industrial–organizational

Industrial and organizational psychology (I–O) applies psychological concepts and methods to optimize human potential in the workplace. Personnel psychology, a subfield of I–O psychology, applies the methods and principles of psychology in selecting and evaluating workers. I–O psychology's other subfield, organizational psychology, examines the effects of work environments and management styles on worker motivation, job satisfaction, and productivity.[75]

Social

Social psychology is the study of how humans think about each other and how they relate to each other. Social psychologists study such topics as the influence of others on an individual's behavior (e.g. conformity, persuasion), and the formation of beliefs, attitudes, and stereotypes about other people. Social cognition fuses elements of social and cognitive psychology in order to understand how people process, remember, or distort social information. The study of group dynamics reveals information about the nature and potential optimization of leadership, communication, and other phenomena that emerge at least at the microsocial level. In recent years, many social psychologists have become increasingly interested in implicit measures, mediational models, and the interaction of both person and social variables in accounting for behavior. The study of human society is therefore a potentially valuable source of information about the causes of psychiatric disorder. Some sociological concepts applied to psychiatric disorders are the social role, sick role, social class, life event, culture, migration, social, and total institution.[77]

Positive

Positive psychology derives from Maslow'shumanistic psychology. Positive psychology is a discipline that utilizes evidence-based scientific methods to study factors that contribute to human happiness and strength. Different from clinical psychology, positive psychology is concerned with improving the mental well-being of healthy clients. Positive psychological interventions now have received tentative support for their beneficial effects on clients. In 2010 Clinical Psychological Review published a special issue devoted to positive psychological interventions, such as gratitude journaling and the physical expression of gratitude. There is, however, a need for further research on the effects of interventions. Positive psychological interventions have been limited in scope, but their effects are thought to be superior to that of placebos, especially with regard to helping people with body image problems.

Psychologists may conduct basic research aiming for further understanding in a particular area of interest in psychology, or conduct applied research to solve problems in the clinic, workplace or other areas. Masters level clinical programs aim to train students in both research methods and evidence-based practice. Professional associations have established guidelines for ethics, training, research methodology and professional practice. In addition, depending on the country, state or region, psychological services and the title "psychologist" may be governed by statute and psychologists who offer services to the public are usually required to be licensed.

Qualitative and quantitative research

Research in most areas of psychology is conducted in accord with the standards of the scientific method. Psychological researchers seek the emergence of theoretically interesting categories and hypotheses from data, using qualitative or quantitative methods (or both).

Controlled experiments

Flowchart of four phases (enrollment, intervention allocation, follow-up, and data analysis) of a parallel randomized trial of two groups, modified from the CONSORT 2010 Statement[79]

Experimental psychological research is conducted in a laboratory under controlled conditions. This method of research relies on the application of the scientific method to understand behavior. Experimenters use several types of measurements, including rate of response, reaction time, and various psychometric measurements. Experiments are designed to test specific hypotheses (deductive approach) or evaluate functional relationships (inductive approach). A true experiment with random allocation of subjects to conditions allows researchers to infer causal relationships between different aspects of behavior and the environment. In an experiment, one or more variables of interest are controlled by the experimenter (independent variable) and another variable is measured in response to different conditions (dependent variable). Experiments are one of the primary research methods in many areas of psychology, particularly cognitive/psychonomics, mathematical psychology, psychophysiology and biological psychology/cognitive neuroscience.

Experiments on humans have been put under some controls, namely informed and voluntary consent. After World War II, the Nuremberg Code was established because of Nazi abuses of experimental subjects. Later, most countries (and scientific journals) adopted the Declaration of Helsinki. In the U.S., the National Institutes of Health established the Institutional Review Board in 1966, and in 1974 adopted the National Research Act (HR 7724). All of these measures encouraged researchers to obtain informed consent from human participants in experimental studies. A number of influential studies led to the establishment of this rule; such studies included the MIT and Fernald School radioisotope studies, the Thalidomide tragedy, the Willowbrook hepatitis study, and Stanley Milgram's studies of obedience to authority.

Researchers in psychology may also use a quasi-experimental design because random assignment to rival intervention/treatment conditions is not possible. For example, in research on the best way to affect reading achievement in the first three grades of school, school administrators may not permit educational psychologists to randomly assign children to phonics and whole language classrooms, in which case the psychologists must work with preexisting classroom assignments. Psychologists will compare the achievement of children attending phonics and whole language classes.

Survey questionnaires

Statistical surveys are used in psychology for measuring attitudes and traits, monitoring changes in mood, checking the validity of experimental manipulations, and for a wide variety of other psychological topics. Most commonly, psychologists use paper-and-pencil surveys. However, surveys are also conducted over the phone or through e-mail. Increasingly, web-based surveys are being used in research for its convenience and also to get a wide range of participants. Similar methodology is also used in applied setting, such as clinical assessment and personnel assessment.

Longitudinal studies

Longitudinal studies are often used in psychology to study developmental trends across the life span, and in sociology to study life events throughout lifetimes or generations. The reason for this is that unlike cross-sectional studies, longitudinal studies track the same people, and therefore the differences observed in those people are less likely to be the result of cultural differences across generations. Because of this benefit, longitudinal studies make observing changes more accurate and they are applied in various other fields.

Because most longitudinal studies are observational, in the sense that they observe the state of the world without manipulating it, it has been argued that they may have less power to detect causal relationships than do experiments. They also suffer methodological limitations such as from selective attrition because people with similar characteristics may be more likely to drop out of the study making it difficult to analyze.

Observation in natural settings

Phineas P. Gage survived an accident in which a large iron rod was driven completely through his head, destroying much of his brain's left frontal lobe, and is remembered for that injury's reported effects on his personality and behavior.[80]

Just as Jane Goodall studied chimpanzee social and family life by careful observation of chimpanzee behavior in the field, psychologists conduct observational studies of ongoing human social, professional, and family life. Sometimes the participants are aware they are being observed, and other times the participants do not know they are being observed. Strict ethical guidelines must be followed when covert observation is being carried out.

Qualitative and descriptive research

Artificial neural network with two layers, an interconnected group of nodes, akin to the vast network of neurons in the human brain.

Research designed to answer questions about the current state of affairs such as the thoughts, feelings, and behaviors of individuals is known as descriptive research. Descriptive research can be qualitative or quantitative in orientation. Qualitative research is descriptive research that is focused on observing and describing events as they occur, with the goal of capturing all the richness of everyday behavior and with the hope of discovering and understanding phenomena that might have been missed if only more cursory examinations have been made.

Computational modeling

The experimenter (E) orders the teacher (T), the subject of the experiment, to give what the latter believes are painful electric shocks to a learner (L), who is actually an actor and confederate. The subject believes that for each wrong answer, the learner was receiving actual electric shocks, though in reality there were no such punishments. Being separated from the subject, the confederate set up a tape recorder integrated with the electro-shock generator, which played pre-recorded sounds for each shock level etc.[81]

Computational modeling[82] is a tool often used in mathematical psychology and cognitive psychology to simulate a particular behavior using a computer. This method has several advantages. Since modern computers process information extremely quickly, many simulations can be run in a short time, allowing for a great deal of statistical power. Modeling also allows psychologists to visualize hypotheses about the functional organization of mental events that couldn't be directly observed in a human.

Several types of modeling are used to study behavior. Connectionism uses neural networks to simulate the brain. Another method is symbolic modeling, which represents many mental objects using variables and rules. Other types of modeling include dynamic systems and stochastic modeling.

Animal studies

Animal experiments aid in investigating many aspects of human psychology, including perception, emotion, learning, memory, and thought, to name a few. In the 1890s, Russian physiologist Ivan Pavlov famously used dogs to demonstrate classical conditioning. Non-human primates, cats, dogs, pigeons, rats, and other rodents are often used in psychological experiments. Ideally, controlled experiments introduce only one independent variable at a time, in order to ascertain its unique effects upon dependent variables. These conditions are approximated best in laboratory settings. In contrast, human environments and genetic backgrounds vary so widely, and depend upon so many factors, that it is difficult to control important variables for human subjects. Of course, there are pitfalls in generalizing findings from animal studies to humans through animal models.[83]

Criticism

Replication crisis

Psychology has recently found itself at the center of a "replication crisis" due to some research findings proving difficult to replicate. Replication failures are not unique to psychology and are found in all fields of science. However, several factors have combined to put psychology at the center of the current controversy. Much of the focus has been on the area of social psychology, although other areas of psychology such as clinical psychology have also been implicated.

Firstly, questionable researcher practices (QRP) have been identified as common in the field. Such practices, while not intentionally fraudulent, involve converting undesired statistical outcomes into desired outcomes via the manipulation of statistical analyses, sample size or data management, typically to convert non-significant findings into significant ones.[84] Some studies have suggested that at least mild versions of QRP are highly prevalent.[85]False positive conclusions, often resulting from the pressure to publish or the author's own confirmation bias, are an inherent hazard in the field, requiring a certain degree of skepticism on the part of readers.[86]

Secondly, psychology and social psychology in particular, has found itself at the center of several recent scandals involving outright fraudulent research. Most notably the admitted data fabrication by Diederik Stapel[87] as well as allegations against others. However, most scholars acknowledge that fraud is, perhaps, the lesser contribution to replication crises.

Third, several effects in psychological science have been found to be difficult to replicate even before the current replication crisis. For example the scientific journal Judgment and Decision Making has published several studies over the years that fail to provide support for the unconscious thought theory. Replications appear particularly difficult when research trials are pre-registered and conducted by research groups not highly invested in the theory under questioning.

These three elements together have resulted in renewed attention for replication supported by Kahneman. Scrutiny of many effects have shown that several core beliefs are hard to replicate. A recent special edition of the journal Social Psychology focused on replication studies and a number of previously held beliefs were found to be difficult to replicate.[88] A 2012 special edition of the journal Perspectives on Psychological Science also focused on issues ranging from publication bias to null-aversion that contribute to the replication crises in psychology[89]

Scholar James Coyne has recently written that many research trials and meta-analyses are compromised by poor quality and conflicts of interest that involve both authors and professional advocacy organizations, resulting in many false positives regarding the effectiveness of certain types of psychotherapy.[90]

It is important to note that this replication crisis does not mean that psychology is unscientific. Rather, this process is a healthy if sometimes acrimonious part of the scientific process in which old ideas or those that cannot withstand careful scrutiny are pruned.[91] The consequence is that some areas of psychology once considered solid, such as social priming, have come under increased scrutiny due to failed replications.[92]

Theory

Criticisms of psychological research often come from perceptions that it is a "soft" science. Philosopher of science Thomas Kuhn's 1962 critique[93] implied psychology overall was in a pre-paradigm state, lacking the agreement on overarching theory found in mature sciences such as chemistry and physics.

Because some areas of psychology rely on research methods such as surveys and questionnaires, critics have asserted that psychology is not an objective science. Other concepts that psychologists are interested in, such as personality, thinking, and emotion, cannot be directly measured[94] and are often inferred from subjective self-reports, which may be problematic.[95][96]

Sometimes the debate comes from within psychology, for example between laboratory-oriented researchers and practitioners such as clinicians. In recent years, and particularly in the U.S., there has been increasing debate about the nature of therapeutic effectiveness and about the relevance of empirically examining psychotherapeutic strategies.[98]

Practice

Psychology Wiki snap shot

Some observers perceive a gap between scientific theory and its application—in particular, the application of unsupported or unsound clinical practices.[99] Critics say there has been an increase in the number of mental health training programs that do not instill scientific competence.[100] One skeptic asserts that practices, such as "facilitated communication for infantile autism"; memory-recovery techniques including body work; and other therapies, such as rebirthing and reparenting, may be dubious or even dangerous, despite their popularity.[101] In 1984, Allen Neuringer made a similar point[vague] regarding the experimental analysis of behavior.[102]

Ethical standards

Current ethical standards of psychology would not permit some studies to be conducted today. These human studies would violate the Ethics Code of the American Psychological Association, the Canadian Code of Conduct for Research Involving Humans, and the Belmont Report. Current ethical guidelines state that using non-human animals for scientific purposes is only acceptable when the harm (physical or psychological) done to animals is outweighed by the benefits of the research.[103] Keeping this in mind, psychologists can use certain research techniques on animals that could not be used on humans.

An experiment by Stanley Milgram raised questions about the ethics of scientific experimentation because of the extreme emotional stress suffered by the participants. It measured the willingness of study participants to obey an authority figure who instructed them to perform acts that conflicted with their personal conscience.[104]

Harry Harlow drew condemnation for his "pit of despair" experiments on rhesus macaque monkeys at the University of Wisconsin–Madison in the 1970s.[105] The aim of the research was to produce an animal model of clinical depression. Harlow also devised what he called a "rape rack", to which the female isolates were tied in normal monkey mating posture.[106] In 1974, American literary critic Wayne C. Booth wrote that, "Harry Harlow and his colleagues go on torturing their nonhuman primates decade after decade, invariably proving what we all knew in advance—that social creatures can be destroyed by destroying their social ties." He writes that Harlow made no mention of the criticism of the morality of his work.[107]

University psychology departments have ethics committees dedicated to the rights and well-being of research subjects. Researchers in psychology must gain approval of their research projects before conducting any experiment to protect the interests of human participants and laboratory animals.[108]

Systemic bias

In 1959 statistician Theodore Sterling examined the results of psychological studies and discovered that 97% of them supported their initial hypotheses, implying a possible publication bias.[109][110][111] Similarly, Fanelli (2010)[112] found that 91.5% of psychiatry/psychology studies confirmed the effects they were looking for, and concluded that the odds of this happening (a positive result) was around five times higher than in fields such as space- or geosciences. Fanelli argues that this is because researchers in "softer" sciences have fewer constraints to their conscious and unconscious biases.

In 2010, a group of researchers reported a systemic bias in psychology studies towards WEIRD ("western, educated, industrialized, rich and democratic") subjects.[113] Although only 1/8 people worldwide fall into the WEIRD classification, the researchers claimed that 60–90% of psychology studies are performed on WEIRD subjects. The article gave examples of results that differ significantly between WEIRD subjects and tribal cultures, including the Müller-Lyer illusion.

^"The mission of the APA [American Psychological Association] is to advance the creation, communication and application of psychological knowledge to benefit society and improve people's lives"; APA (2010). About APA. Retrieved 20 October 2010.

^Bureau of Labor Statistics, U.S. Department of Labor, Occupational Outlook Handbook, 2010–11 Edition, Psychologists, on the Internet at bls.gov (visited 8 July 2010).

^Cecilia Taiana, "Transatlantic Migration of the Disciplines of Mind: Examination of the Reception of Wundt's and Freud's Theories in Argentina", in Brock (ed.), Internationalizing the History of Psychology (2006).

^ abcIrina Sirotkina and Roger Smith, "Russian Federation", in Baker (ed.), Oxford Handbook of the History of Psychology (2012).

^Windholz, G. (1997). "Ivan P. Pavlov: An overview of his life and psychological work". American Psychologist52 (9): 941–946. doi:10.1037/0003-066X.52.9.941.

^ abIrmingard Staeuble, "Psychology in the Eurocentric Order of the Social Sciences: Colonial Constitution, Cultural Imperialist Expansion, Postcolonial Critique" in Brock (ed.), Internationalizing the History of Psychology (2006).

^Leichsenring, Falk; Leibing, Eric (2003). "The effectiveness of psychodynamic therapy and cognitive behavior therapy in the treatment of personality disorders: A meta-analysis". The American Journal of Psychiatry160 (7): 1223–33. doi:10.1176/appi.ajp.160.7.1223. PMID12832233.

^Jensen, J.P.; Bergin, A.E.; Greaves, D.W. (1990). "The meaning of eclecticism: New survey and analysis of components". Professional Psychology: Research and Practice21 (2): 124–30. doi:10.1037/0735-7028.21.2.124.

^Booth, Wayne C. Modern Dogma and the Rhetoric of Assent, Volume 5, of University of Notre Dame, Ward-Phillips lectures in English language and literature, University of Chicago Press, 1974, p. 114. Booth is explicitly discussing this experiment. His next sentence is, "His most recent outrage consists of placing monkeys in 'solitary' for twenty days—what he calls a 'vertical chamber apparatus .... designed on an intuitive basis' to produce 'a state of helplessness and hopelessness, sunken in a well of despair.'"